The present invention is related to regeneration of spent or deactivated catalysts used in hydroprocessing hydrocarbon-containing feedstocks, and, more particularly, to a method for regenerating deactivated catalysts employed in hydrotreating, including hydrodesulfurization and hydrodenitrogenation.
Hydroprocessing of hydrocarbons is usually carried out with a particulate catalyst comprised of a porous refractory oxide support containing catalytically active components such as Group VIB and Group VIII metals, and occasionally phosphorus components. Typically, such catalysts comprising nickel, molybdenum and phosphorus components supported on alumina are employed in hydrotreating hydrocarbon-containing feedstocks so as to reduce high concentrations of sulfur and nitrogen. Although these catalysts are highly useful in reducing sulfur and nitrogen from hydrocarbon-containing feedstocks, the activity of such catalysts is diminished during the course of processing as a result of deposition of carbonaceous(carbon or coke-containing) and/or sulfur residues on the catalyst. Such carbonaceous and sulfur deposits reduces the effective surface area and pore volume of the catalyst and tend to poison the catalyst and plug the pores. During the course of processing, the operating temperature must be increased to compensate for the coking, plugging and poisoning effects, but the higher temperature increases coking and further deactivates the catalyst. Eventually, the required temperature increase to maintain a desired amount of sulfur and nitrogen removal becomes intolerable, and the catalyst is removed, deactivated due to carbonaceous and/or sulfur deposits.
Regeneration of coked and sulfur-contaminated catalysts back to a catalytically active form has been the subject of much investigation, and a number of approaches for regenerating hydroprocessing catalyst by removal of coke and sulfur have been developed. In one regeneration method, the deactivated catalyst is soaked in water for more than one hour prior to removal of the contaminants. However, such an approach (1) does not restore a sufficiently high degree of catalytic activity, (2) results in unacceptable agglomeration of active metals, or (3) results in an unacceptable loss of catalytically active metals, such that catalytic activity of the regenerated catalyst is considerably inferior to the fresh catalyst.
Accordingly, new methods are still being sought for regenerating a catalyst, particularly a hydroprocessing catalyst, such that carbonaceous(coke containing) and sulfur deposits are effectively removed and no appreciable loss of catalytically active metals and substantial recovery of catalytic activity result.